Chest
Volume 105, Issue 2, February 1994, Pages 469-474
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Clinical Investigations
Home Care and Rehabilitation
Prognosis of Severely Hypoxemic Patients Receiving Long-term Oxygen Therapy

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Two hundred seventy severely hypoxemic (PaO2 ≤ 55 mm Hg: mean ± SD = 48 ± 6) COPD patients (232 men) were selected for long-term oxygen therapy (LTOT). They were old (mean = 66 ± 8 years), with severe airflow limitation (FEV1 = 30 ± 12 percent of predicted), some CO2 retention (PaCO2 = 47 ± 9 mm Hg), and compensated respiratory acidosis. Eighteen percent of the patients presented some complicating pleuropulmonary diseases (pleural thickening, sequelae of tuberculosis, etc). Overall survival proportion was poor: 70, 50, and 43 percent at 1, 2, and 3 years, respectively. The Cox model showed that the factors which independently reduced survival were lower CO transfer coefficient, smaller intrathoracic gas volume, more severe bronchial obstruction, the fact that oxygen administration did not increase PaO2 above 65 mm Hg, increasing age, and the presence of chest wall abnormalities. When the patients were divided into three groups according to mortality risk, the mean clinical and functional profile of the high-mortality risk group was consistent with the prevalence of emphysematous lesions. Moreover, the best survivors fitted better into the “bronchitic” type; they showed a higher mean PaCO2, suggesting that some degree of hypoventilation could delay muscular fatigue and improve survival. The difference in the proportion of “emphysematous” and “bronchitic” patients is a possible explanation for the variability of the mortality rate reported in literature.

Section snippets

Patients

The patients were admitted to three hospitals from 1985 to 1990 with respiratory insufficiency and severe hypoxemia. Most were admitted for an acute exacerbation of airflow obstruction, some with right heart failure. After recovery, they were assessed during several weeks for clinical stability.

According to the Belgian Social Security regulations for reimbursement of LTOT, the patients were selected for oxygen treatment if their PaO2 while breathing air was equal to or lower than 55 mm Hg in a

Results

On an average, the patients were old (mean age, 66 ± 8 years), with severe airway obstruction (FEV1 = 30 ± 12 percent of predicted values) and pulmonary hyperdistention (intrathoracic gas volume [ITGV] = 151 ± 44 percent). The mean transfer coefficient TLCO/VA of the patients able to perform the maneuver was reduced to 57 ± 31 percent of predicted.

The patients were severely hypoxemic with some CO2retention and compensated respiratory acidosis (Table 1). Oxygen breathing drastically improved the

Discussion

The mean PaO2 while breathing air (48 ± mm Hg) of the patients from the present series was lower than that of other LTOT series5, 6, 7,11,17,18,35 where mean PaO2 exceeded 50 mm Hg. Under O2 therapy, our patients and those from the MRC reached, nevertheless, a slightly higher PaO2 than in the other series. As far as PaCO2 is concerned, most studies report, as we do, a moderate hypercapnia,6, 7, 8,11,15,18,19 while others5, 13, 14 show a mean PaCO2 within normal limits. All of the studies

Conclusion

In conclusion, the mortality rate of our severely hypoxemic COPD patients (PaO2 ≤ 55 mm Hg) remained considerably high, in spite of LTOT. According to the Cox model, the best predictors of a poor outcome were the following: a low TLCO/VA, a small ITGV, a severe airflow limitation, the fact that O2 therapy does not increase PaO2 above 65 mm Hg, and, from the clinical point of view, increasing age, and the presence of chest wall abnormalities.

The clinical and functional profile of the patients,

ACKNOWLEDGMENTS

The authors wish to thank their colleagues L. Delaunois, Y. Sibille, and P. Weynants for providing the records of many patients; the technical staff: J. P. Delwiche, F. Wautelet, F. Licope, F. Wanthier, F. Pirson, Cl. Goffin, and J. Duplicy; and M. Laureys for improving the English style of the paper and preparing the typescript.

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    revision accepted May 28.

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